Heat insulating wall construction for a low temperature liquefied gas tank of the membrane type

ABSTRACT

A heat insulating wall construction for a membrane type low temperature liquefied gas tank includes a plurality of support members extending in parallel with each other between the inner membranous vessel and the outer rigid vessel. A laminated wood plate is fixed on the inner ends of the support members. Heat insulating material is charged in the space formed among the support members between the laminated wood plate and the outer rigid vessel. The laminated wood plate is composed of inner and outer layers with the joints of the respective layers positioned out of alignment with each other. All the components in the wall construction are bound together by means of adhesives and nails.

United States Patent Yamamoto et al.

[ HEAT INSULATING WALL CONSTRUCTION FOR A LOW TEMPERATURE LIQUEFIED GAS TANK OF THE MEMBRANE TYPE [72] Inventors: Katsuro Yamamoto, Tokyo; Ku-

niyoshi Obata, Kawasaki; Toru Sata, Kamakura, all of Japan [73] Assignee: Bridgestone Liquefied Gas Company, Ltd., Tokyo, Japan [22] Filed: Aug. 18, 1970 [21] Appl. No.: 64,671

[58] Field of Search ..52/425, 426, 424, 404, 249, 52/615, 664, 665, 743, 480, 592

[56] References Cited UNITED STATES PATENTS 318,870 5/1885 Chase ..52/404 451 Oct. 3, 1972 Primary Examiner-Price C. Faw, Jr. Attorney-Waters, Roditi, Schwartz & Nissen ABSTRACT A heat insulating wall construction for a membrane type low temperature liquefied gas tank includes a plurality of support members extending in parallel with each other between the inner membranous vessel and the outer rigid vessel. A laminated wood plate is fixed on the inner ends of the support members. Heat insulating material is charged in the space formed among the support members between the laminated wood plate and the outer rigid vessel. The laminated wood plate is composed of inner and outer layers with the joints of the respective layers positioned out of alignment with each other. All the components in the wall construction are bound together by means of adhesives and nails.

2 Claims, 3 Drawing Figures PATENTEDocr 3 m2 SHEET 2 BF 2 FIG. 2

HEAT INSULATING WALL CONSTRUCTION FOR A LOW TEMPERATURE LIQUEFIED GAS TANK OF THE MEMBRANE TYPE The present invention relates to a heat insulating wall, and more particularly to a heat insulating wall to be used in a membrane type tank for containing low temperature liquefied gas such as liquefied petroleum gas which, being normally in the gaseous state at room temperatures, is liquefied at a low temperature under atmospheric pressure.

The low temperature liquefied gas storage tank of the type described above is well known in the art and generally has a heat insulating wall between the inner membranous vessel and the outer rigid vessel. On account of the fact that the internal pressure on the inner membranous vessel is transmitted to the outer rigid vessel through the heat insulating wall, the heat insulating material constituting the heat insulating wall is required to have compressive resistance. In view of the above fact, the heat insulating wall in the conventional membrane type tank has been made of a heat insulating material having a compressive strength such as hard foamed polyurethane and the like. Such heat insulating material having compressive strength, however, is disadvantageous in that it is expensive, which results in considerable increase in the manufacturing costs of the whole tank.

Another disadvantage inherent in the construction of the conventional type of the liquefied gas tank is that a secondary barrier has been separately provided in the heat insulating wall construction in order to temporarily prevent the leakage of the liquefied gas in the event that the liquefied gas leaks out from the inner vessel. And the secondary barrier has been made of low temperature resistive metal. Therefore, it has taken much time and labor to make the heat insulating wall. On account of the above fact and due to the high material cost as well, the manufacturing cost of the tank has been very expensive. Under the above-described conventional disposition of the liquefied gas tank of the membrane type, a new or improved tank has been awaited in which the heat insulating material per se is not required to have compressive strength and no separate secondary barrier is required to be incorporated.

In light of the foregoing observations and description, it is an object of the present invention to provide a heat insulating wall for a membrane type low temperature liquefied gas tank in which a plurality of support members are incorporated in the wall construction so that the heat insulating material per se is not required to have compressive strength.

It is also an object of the present invention to provide a heat insulating wall for a membrane type low temperature liquefied gas tank in which laminated wood is incorporated in the wall construction as a secondary barrier so that no separate secondary barrier may be required to be incorporated. v

Another object of the present invention is to provide a heat insulating wall for a membrane type low temperature liquefied gas tank in which the laminated wood is composed of an inner layer and an outer layer stuck together with adhesives with the joints of the respective layers positioned out of alignment with each other so that the laminated wood serving as a secondary barrier may have sufficient strength against the internal stress caused by temperature variations.

Still another object of the present invention is to provide a heat insulating wall for a membrane type low temperature liquefied gas tank which is made of wood for the most part thereof so that the heat insulating wall as a whole may not lose its heat insulating property.

A further object of the present invention is to provide a heat insulating wall for a liquefied gas tank which has a much improved liquid-tight property by the use of doubled-layer laminated wood with the joints of the respective layers positioned out of alignment with each other.

A still further object of the present invention is to provide a heat insulating wall for a liquefied gas tank having remarkably high strength as a whole by the use of nails together with adhesives.

In order to achieve the above described objects of the invention, the heat insulating wall in accordance with the present invention includes a plurality of support members fixed to the outer vessel at one end and extending in perpendicular thereto. The ends of the support members on the inner side are connected with one another by means of a wooden framework. On the wooden framework is provided laminated wood composed of inner and outer layers with the joints of the respective layers positioned out of alignment with each other. Heat insulating material is disposed in the space between the laminated wood and the other rigid vessel.

In accordance with the heat insulating wall of the present invention constructed as described hereinabove, the heat insulating material is not required to have compressive strength since it only fills up a space formed with rigid support members. Since the laminated wood serves as a secondary barrier to prevent the leakage of the liquefied gas, there is no need to provide a separate secondary barrier made of metal or the like. Thus, the heat insulating wall of the present invention is of simple construction yet can be easily manufactured at low cost.

Various other objects, features and advantages of the present invention will be made apparent by reference to the following detailed description of a preferred embodiment thereof, reference being made to the accompanying drawings, in which:

FIG. 1 is a perspective view of the basic construction of the heat insulating wall in accordance with an embodiment of the present invention;

FIG. 2 is a fragmentary side elevational view of the basic construction of the heat insulating wall partly in section, taken in the direction of the arrow A of FIG. 1; and

FIG. 3 is an explanatory plan view showing the construction of the laminated wood incorporated in the heat insulating wall in accordance with the present invention.

Referring now to FIG. 1, the basic construction of the heat insulating wall on which the heat insulating material, laminated wood serving as a secondary barrier and the inner membranous vessel are to be mounted is shown. On the inner surface of the rigid outer vessel 1, a steel plate 2 is fixed, on which a plurality of channel members 3 are welded in parallel relation with each other. A plurality of support members 4 are fixed by bolts and nuts at the lower end portion thereof to the channel members 3 and stand close together on the rigid outer vessel 1 of the tank.

On the top ends of the support members 4 is mounted a wooden framework 6 constructed with large beams 6a and small beams 6b assembled in a lattice construction. The intersections of the lattice are positioned just above the support members 4. The large beams 6a are secured to the head of the support members 4 with plywood joint plates 7 by means of adhesives and nails.

The top surface of the large beam 6a is made flush with the top surface of the small beam 6b so that the top surface of the framework 6, the surface facing inward the tank, may make a smooth single plane. On this top surface of the framework 6, a laminated wood plate 8 composed of an outer layer 8a and an inner layer 8b is mounted as shown in F IG. 2. The outer and inner layers 8a, 8b are made of plywood respectively. As clearly shown in FIG. 2, a membrane 9 constituting an inner vessel covers the inner layer 8b of the laminated wood plate 8. I

The outer layer 8a of the laminated wood plate 8 is fixed to the top surface of the framework 6 by means of adhesives and nails. The inner layer 8b is also fixed to the outer layer 8a by means of adhesives and'nails.

The outer layer 8a and the inner layer 8b of the laminated wood plate 8 are so arranged that the joints of the respective layers consisting of a plurality of rectangular pieces of wooden plates may be on the beams of the framework 6 and that the joints of the outer layer 8a may be out of alignment with the joints of the inner layer 8b as shown in FIG. 3. Thus, the laminated wood plate 8 as a whole has no joints extending from inside to outside.

In the space formed among the support members 4 between the laminated wood plate 8 and the rigid outer vessel 1, proper heat insulating material such as perlite powder is charged.

The heat insulating wall constructed as described above has a variety of advantages as follows:

1. The laminated wood plate 8 integrally incorporated in the heat insulating wall serves as the secondary barrier for preventing the leakage of the liquefied gas. Since the secondary barrier is composed of an outer layer 8a and an inner layer 8b tightly stuck with each other by means of adhesives and nails, the internal stress caused by the temperature variation is treated as a shearing stress at the stuck surface of the layers. Accordingly, the water tight property of the secondary barrier is maintained to a high degree.

2. Since the internal pressure in the inner membrane vessel 9 is transmitted to the outer rigid vessel 1 through the laminated wood plate 8, framework 6 and the support members 4, the heat insulating material charged in the wall is not required to have compressive strength. Thus, cheap heat insulating material can be employed.

3. Since the basic construction of the wall comprising the laminated wood plate 8, framework 6 and support members 4 is made of wood having comparatively low heat conductivity, there is no fear of losing the heat insulating property on account of its basic construction. 4. Since the outer layer 8a and the inner layer 8b of the laminated wood plate 8 are so arranged that the joints of the rectangular components of the respective layers may not be in alignment with each other, there is no fear of leaking therethrough. If there should be some leakage through the joint of the inner layer 8b, it is almost impossible for the leaked liquefied gas to reach the outer surface of the outer layer 8a because the path from the inner joint to the outer joint is long and filled with adhesives.

5. Since the components in the wall of the present invention are combined together by means of not only adhesives but also nails for providing the necessitated pressure on the surfaces with adhesives sandwitched therebetween, the construction as a whole is considerably strong against the external force exerted thereon.

6. The joint plates 7 combining the large beams 6a with the support members 4 have the additional effect of preventing the support members 4 from thrusting into the large beams 6a by dispersing the load exerted onto the large beams 6a.

While a certain preferred embodiment of the invention has been specifically illustrated and described hereinabove, it will be understood that the invention is not limited thereto as many variations will be apparent to those skilled in the art.

For instance, a steel plate 2 is welded onto the surface of the channel members 3 for protecting the heat insulating wall from moisture in the case where the wall construction is made outdoors. But it will be apparent to those skilled in he art that the steel plate can be eliminated in the case that the wall construction is made directly in the rigid outer vessel.

Furthermore, it will be also apparent that the framework and the support members in the above described embodiment can be reinforced with auxiliary supporting members and the like.

Thus, it should be understood that various additional modifications are possible in the arrangement and construction of its components without departing from the scope of the invention.

What is claimed is:

1. In a low temperature liquefied-gas tank of the membrane type, a heat insulating wall structure, said structure comprising a framework constituted of support members formed of a load supporting and heat insulating material, said framework defining a thickness of the heat insulating wall structure having the spaces formed adapted to be filled with a heat insulating material, and a plate member fastened to and extending over the framework to define an inner surface of the heat insulating wall structure, said framework forming a network comprising a plurality of contiguously arranged flush surfaces, said plate member comprising a plurality of contiguous first plate elements each being supported along at least portions of its periphery by said surfaces, a plurality of contiguous second plate elements being superimposed on said first plate elements in close surface contact therewith, the joints between contiguous of said second plate elements being offset relative to the joints between contiguous of said first plate elements, said framework being substantially constituted of said network, including support members extending between a wall of a rigid outer vessel and said network substantially perpendicularly to said wall and said network, said network being composed of a first group of parallel extending beams, a second group of parallel extending beams smaller than said first beams, said second beams being arranged to extend perpendicularly to said first beams, said support members being connected with said first group of beams at bridging said support members and said first group of beams.

2. A wall structure according to claim 1, comprising channel members for fastening members to the wall of portions where said first and second beams cross each, 5 said rigid Outer Vessel- 

1. In a low temperature liquefied-gas tank of the membrane type, a heat insulating wall structure, said structure comprising a framework constituted of support members formed of a load supporting and heat insulating material, said framework defining a thickness of the heat insulating wall structure having the spaces formed adapted to be filled with a heat insulating material, and a plate member fastened to and extending over the framework to define an inner surface of the heat insulating wall structure, said framework forming a network comprising a plurality of contiguously arranged flush surfaces, said plate member comprising a plurality of contiguous first plate elements each being supported along at least portions of its periphery by said surfaces, a plurality of contiguous second plate elements being superimposed on said first plate elements in close surface contact therewith, the joints between contiguous of said second plate elements being offset relative to the joints between contiguous of said first plate elements, said framework being substantially constituted of said network, including support members extending between a wall of a rigid outer vessel and said network substantially perpendicularly to said wall and said network, said network being composed of a first group of parallel extending beams, a second group of parallel extending beams smaller than said first beams, said second beams being arranged to extend perpendicularly to said first beams, said support members being connected with said first group of beams at portions where said first and second beams cross each, and reinforcing joint plates being fastened to and bridging said support members and said first group of beams.
 2. A wall structure according to claim 1, comprising channel members for fastening members to the wall of said rigid outer vessel. 